Projectile broach



C W. MUSSER PROJECTILE BROACH Filed May 20, 1960 INVENTCR. C WALTONMUSSER Q. JQ M M BY ijfloimii ATTORNEYS Oct. 9, 1962 United StatesPatent Ofiice 3,057,264 Patented Oct. 9, 1962 3,057,264 PROJECTILEBROACH C Walton Musser, Beverly, Mass, assignor to the United States ofAmerica as represented by the Secretary of the Army Filed May 20, 1960,Ser. No. 30,692 1 Claim. (Cl. 90-63) (Granted under Title 35, US. Code(1952), see. 266) The invention described herein may be manufactured andused by or for the Government for governmental purposes without thepayment to me of any royalty thereon.

This invention relates to the manufacture of firearms, and moreparticularly to a device which functions in response to the firing of anexplosive charge to rifle the interior of a gun barrel.

Heretofore the rifiing of a gun barrel has usually involved the use of acutting tool fixed to the end of an arm adapted to be extended into thebore of the gun. The present invention simplifies and greatly expeditesthis procedure by the provision of an improved rifle cutting devicewhich functions in response to the firing of an explosive charge. In apreferred embodiment of the invention, [the cutting element of thedevice is in the form of a projectile having a cylindrical forwardportion which is a close fit to the barrel and a rearward portionprovided with cutting teeth having a lead designed to give the desiredtwist to the rifling.

The invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawings and itsscope is indicated by the appended claim.

Referring to the drawings:

FIG. 1 shows a longitudinal section of a gun containing a projectile andcartridge case according to this invention.

FIG. 2 is a longitudinal section through the projectile alone.

FIG. 3 is an enlarged longitudinal section of the cutting teeth.

FIG. 4 is a top plan developed view showing a rear portion of the leadand teeth of FIG. 3.

FIGS. 1 to 3 illustrate a conventional recoilless rifle which includes abarrel 10, a chamber 11 and venturi 12. Extending through the chamber 11is a cartridge which includes a casing 13 enclosing an explosive chargeand a projectile 14. This projectile has walls of about the wallthickness of a recoilless rifle lbarrel as shown in the herein drawing.

The projectile 14 has on its rearward surface teeth 15 (FIGS. 1, 2 and3) which are similar to the teeth of a broach and have a lead designedto give a desired twist to the rifiing. The forward surface of theprojectile has no teeth and functions to guide the breach through therifle tube.

In practicing the invention, the cartridge 13--14 is fired in the samemanner as a conventional cartridge. The device is especially usefulwhere a shallow-groove rifling is required to give a fin stabilizedprojectile a slight twist to prevent ya-w. An advantage in theillustrated construction is that the cutting teeth 15 are protectedduring shipment and handling by the cartridge case 13 which in usualpractice is of a softer metal than the projectile itself. As shown,approximately the rear half and heavier duty part projectile teeth havea more rigid support than do the fore portions because these projectileteeth are located over and nearer the solid base of the projectile,while the fore portion of teeth 15 are radially outside a hollowedcentral portion. The close fitting cylindrical guide portion 16 of theprojectile is advantageously close to the cutting teeth 15. Theperforations in casing 13 are for the usual purpose for their use inrecoilless weap ons, but here these perforations are located in rear ofthe cutting teeth, which teeth are protected by imperforate casematerial as shown.

I claim:

In a round for cutting rifling grooves in the barrel of a recoillessrifle for firing a fin and spin stabilized projectile, the combinationtherewith of the improvement adapting said cutting round for use in arecoilless weapon, said round comprising a projectile having an axialhollow portion having walls of about the wall thickness of a recoillessrifle barrel in which rifiing grooves are to be cut by firing saidround, said hollow portion extending for a major portion of the lengthof said projectile from its front end, cutting teeth on approximately arear half of the length of the projectile and extending over a solidbase portion and forward thereof, a forward portion of said projectilebeing a guide of a size to closely fit within a barrel of a gun and beclosely adjacent said cutting teeth to reduce the danger of any bucklingoccurring when a rifle groove cutter is being pushed, the cutting teethhaving a lead for cutting rifiing grooves in a gun barrel with the teethbeing of increasing diameter toward the rear, and said cutting roundincluding a cartridge case of usual case material and having a forwardimperforate portion covering said teeth with a perforate portion in rearof said projectile, to enclose a propellant charge.

References Cited in the file of this patent UNITED STATES PATENTS 37,898Bonzano Mar. 17, 1863 599,472 Nobel Feb. 22, 1898 1,394,079 Fuchs Oct.18, 1921 2,641,822 Sampson June 16, 1953 2,994,249 Schecter et al. Aug.1, 1961

